Calcining process and apparatus



Aug. 21, E945. H. c. JESSEN CALCINING PROCESS AND APPARATUS Filed Aug. 4, 1941 6 Sheets-Sheet 1 INYE TOR C A'ITORN Aug, 21, 1945.

H. c. JESSEN CALCINING PRQGESS AND APPARATUS Filed Aug 4, 1941 6 Sheets-Sheet 2 INVENTOR,

ATTORNEYS.

Aug. 21, 1945. H. c. JESSEN I CALCINING PROCESS AND APPARATUS 6 Sheets-Sheet 3 Filed Aug. 4 1941 VEN 0R.

IN fl wa BY. J r- 4,

ATTORN EYS GALCINING PROCESS AND ABPARATUS Filed Aug. 4, 1941 6 Sheets-Sheet 4 INVENTOR- n If y ATI'ORNEY6. z

-7 H. c. JESSEN 2,383,254

GALCINING PROCESS AND APPARATUS Filed Aug. 4, 1941 e Sheets-Sheet s .41 as f: 1 g a- 4a- I 39 7 m I I I 11 r/ f 54. 1g 12 v lNVENTOR- l fl BY. 7 1 I 13 1%! A'r'rbRNEYS.

Aug. 21, 1945. H.'C."JESSEN CALCINING PROCESS AND APPARATUS Filed Aug. 4, 1941 6 Sheets-Sheet 6' hydrate.

under steam pressure.

Patented Aug. 21, 1945 2,383,254 CALCINING PROCESS AND APPARATUS Heinrich C. Jessen, Wilmette, 111., assignor to United States Gypsum Company, Chicago, 111., a corporation of Illinois Application August 4, 1941, Serial No. 495,364

6 Claims.

This invention relates to a method and apparatus for calcining inorganic material and more particularly it relates to a method and apparatus for calcining gypsum rock for the production of calcium sulfate hemihydrate.

- Various processes and apparatuses have heretofore been proposed for effecting the calcination of natural gypsum rock to calcium sulfate hemi- In' Randel and. Dailey Patent No. 1,901,051, issued March 14, 1933, and Randel and Dailey Patent No. 1,931,240, issued October 17,

1933, there has been disclosed a new type of calcium sulfate hemihydrate which had theretofore bee'nunknown. This product is known as alpha gypsum and may be prepared by the calcination of gypsum rock at elevated temperature and V In McNeil Patent No. 1,897,394, issued February 14, 1933, and Randel, Dailey and McNeil Patent No. 2,074,937, issued March 23, 1937, have been disclosed processes and apparatuses for producing alpha gypsum by a pressure calclnation process. These patentees contemplated a vertical cylindrical calcineror calcination chamber'for receiving lump rock gypsum which was calcined therein for several hours under steam pressure. It has been found that pressure calcination has a tendency to cause the lumps of calcined gypsum to adhere together. Reciprocating agitator devices have been proposed to break up the mass of lump calcined gypsum to permit the lumps to flow out through the bottom discharge gate of the calciner. These agitating devices have not been entirely successful and invention, an apparatus has been provided which comprises one or more steam pressure calciners or calcination chambers into which an intact body ered into the calciner.

of material to be calcined may be introduced and subsequently removed without the necessity of discharging it through a bottom discharge orifice in the chamber. Each calciner comprises'an upright shell portion having means for supplying steam thereto under pressure and a removable cover which may be secured thereto to permit a desired steam pressure to be built up therein.

The cover is constructed so that it may be completely removed from over the top of the chamber in order topermita bucket or basket con-' taining the desired gypsum rock charge to be,

passed into and subsequently removed from the calcining zone. In operation, the bucket or basket is charged with raw gypsum rock and low- Th calciner cover is then secured in place andsteam is passed into the oalcination chamber at elevated pressures for several hours in order to efiect desired calcination of the gypsum rock. After the calcination' has been completed, the cover is removed from the calciner and the bucket or basket containing the calcined gypsum is lifted out of the chamber and the ,contents of the bucket or basket may be discharged to any desired point. In accordance with one embodiment of this invention, it is preferable to provide a plurality of the calciners briefly described above so that one of them may be discharged and recharged while calcination is beingeilected in the remaining of them.

sometimes it is necessary to resort to hammering the calciner shell to loosen the lumps and to induce them to flow out through the discharge gate. This hammering of the shell eventually causes breakage and failure of the steel, making replacement of the shell necessa y- An object of this invention, therefore, is to provide a method of and apparatus for the pressure calcination of gypsum Or other inorganic material in which difficulties in discharging the pressure calcination apparatus are avoided.

A further object of this invention is the Provision of a method of and apparatus for the semicontinuous production or calcined gypsum.

A further object of this invention is the provision of a method of and apparatus for the production of alpha gypsum which may be carried out with a minimum of labor and equipment.

Further and additional objects will appear from the following description, the accompanying drawings. and the appended claims.

In accordance with one embodiment of this For amore complete understanding of this iny r vention, reference will now be had to the drawings, in which Fig. l is a diagrammatic elevational view 01' a calcining plant constructed in accordance with one embodiment of this invention indicating in a generalway the steps involved in the treatment of the material;

Fig. 2 is a semi-diagrammatic plan view of a portion of the calcining apparatus indicated gen.- erally in Fig. 1:

Fig, 3 is an elevation of the feeding end of the apparatus constructed in accordance with one embodiment of this invention;

Fig. 4 is a sectional elevation showing the de- Fig. '1 is a sectional plan view through the calciner and bucket taken on the line of Fig. 5;

Fig. 8 is an elevation of a modified form of bucket or basket;

Fig. 9 is a sectional elevation through the bucket shown in Fig. 8 in which the bottom discharge doors have been swung open; and

Fig. 10 shows a modified form of calcination chamber and buckets which may be used in accordance with another embodiment of this invention.

The improved apparatus constructed in ac- "cordance with one embodiment of this invention comprises (see Figs. 1 and 2) a plurality of calciners or calcination chambers III which are preferably arranged in two parallel spaced rows directly underneath a suspended track 43a, a loading station A for charging buckets 38 with raw rock ypsum for the calciners, a delivery station B for discharging the calcined product from the buckets 38, and an overhead crane 43 for lifting and moving the buckets from the calciners and delivering them to and from the loading station andthe delivery station.

Referring now more particularly to Figs. 5, 6

and '7, each calciner or calcination chamber It] comprises a cylindrical shell ll having a down wardly curved bottom portion l2 provided with an external insulation 33. A drainpipe [20. controlled by a trap l3 is connected to the bottom l2 and an inlet steam pipe 34 controlled by valve 35 extends through the side walls of the calciner ID for introducing live steam thereinto. The shell II is provided with legs 36 which serve as a support for the calciner.

' As shown in the drawings, a sealing ring l4is provided around the top of the shell II and an upwardly curved removable cover is removably seated thereon. A suitable gasket I6 is provided to effect a steam-tight connection between the cover l5 and the shell II. The upper edge of the ring I4 is provided with a plurality of inwardly extending lugs I! which mate with outstanding lugs l8 formed on the outer peripheral edge of the cover 55 whereby the lugs 18 on the cover extend under the lugs II on the ring when the cover I5 is in closed and locked position. An arcuate rack. I9 is secured to the top edge of the cover i5 and meshes with a segmental gear 20 pivotally mounted on a pivot 2i associated with an upwardly extending portion of the ring 14. A handle 22 is associated with the gear 20 so that when the handle 22 is rocked about the pivot 2|, the cover 15 will be caused to rotate in a horizontal plane in the sealing ring M. The cover 15 is also provided with a plurality of-rollers 24,

each of which is rotatably mounted on the end of, a spindle 25, the inner end of each spindle be-- ing pivotally mounted on a pivot 26 which is supported on a cover bracket 21. An adjusting bolt 28 in the bracket 21 provides means for raising or lowering the rollers 24 and the coverv l5 supported thereby whereby a steam-tight closure is efiected. The rollers 24 roll on top of the ring I4 when the handle 22 is rocked, thereby rotating the cover 55 and moving the lugs l8 underneath the inwardly extending lugsll positioned on the ring l4 whereby a tight closure is effected.

In order to completely remove the cover l5 from over the top of the calciner I6, an arcuate crane 29 is provided which is pivotally mounted in brackets 36 on the shell II, and is provided with a chain hoist 3| connected by a chain 32 to an eye-bolt 32a on the cover l5 So that the cover l5 may be elevated above the shell ll and the ring l4 and swung to one sideof the shell.

A bucket or basket 38 is provided for each of hook-receiving hole 42. Brackets '41 are provided on the inside of the shell to engage the bottom of the bucket 38 and to support the same when the latter is positioned within the calciner. Spacer flanges 43 are provided on the bucket in order to center the bucket within the shell ll. Extending outwardly from the side walls 39 of the bucket and between th spacer flanges 48 are a pair of diametrically opposed trunnions 63. These trunnions are positioned somewhat less than half way up the sides of the bucket and are used to assist in dumping the same, as will be hereinafter more fully described.

Referring now more particularly to Figs. 1 to 4, an overhead crane 43 carried on 'a track 43a is provided having a chain-suspended bucket ball 44. Chains 45 having hooks 46 are suspended from the outer ends of the ball 44 and the hooks 46 are adapted to engage in th holes 42 of the upwardly extending ears 4| mounted on the side walls of the buckets 38. The overhead crane 43 thereby provides means for lifting the buckets 38 into and' out of the calcination chambers or calciners l0, after the cover l5 has been removed therefrom as has previously been described and the crane 43 may be operated to deliver the buckets between loading station A and delivery station B.

Referring now more particularly to Figs. 1 to 3, the buckets or baskets 38 may be charged with a raw gypsum rock at loading station A. An empty bucket 38 is deposited at loading station A on a platform 48a. by the overhead crane 43. Gypsum rock from crushing and screening operations is carried by a belt 48 to a rock storage bin 58 having a spiral inlet duct 5| for gently depositing the lump rock in the bin 50 without the production of fines due to falling of the lumps.

The bin 56 discharges onto a vibrating screen 52 operated by a motor 52a. which removes last traces of fines which latter have a tendency to cause lumps of the product to adhere together after calcination. The vibrating screen 52 is positioned so that the screened rock, free from fines, is discharged from the screen into the bucket 38 positioned on the platform 48a. A suitable control linkage 53 is provided to open and close a gate 54 in the bottom of the bin 50, so as to control the fiow of rock to the screen. 52 and into the bucket 38.

mounted on said framework, each of said plates having a slot 62 for receiving the dumping trunnions 63 secured to each side of each bucket 38. Thus, as a bucket 38 is lowered by the crane 43 overthe hopper 56 so that the trunnions 63 engage the slots 62, the bucket 38 tilts downwardly and dumps its contents of calcined rock into the hopper 56. A slide gate 65 between the hopper 56 and the bin 51 is perated by a compressed air cylinder 66 to shut the gate 65 after a dumping operation to keep hot the supply of rock within the bin 51. A grizzly screen 8'! above the bin 51 serves to break up any masses of rock that may have been formed during the calcining operation. A- walkway 61a is provided arflacent the l a hopper 56 for theconvenience of the operator.

Referring now more particularly to Fig. 1, a

- conveyor 68 is provided for withdrawing the hot lump calcined rock from the bin 51 and for introducing it into a rotary drier 89 wherein last traces of steam and free water are removed from the hot calcined product. The drier 69 is preferably of the inner tube type to prevent possible further calcination of the gypsumto the anhydrite. A

grinding mill I0, screw-conveying means H and I3, bucket-conveying means 12 and 16, a duct 14, and a tube mill 15 are also provided for further The bucket containing the hot calcined-rock is carried by the overhead craneover the top of the dumping hopper 56 and-positioned so that the trunnions 63 fit into the slots 62 on the ppositely disposed plates 6| mounted on the framework 80. Inasmuch as the center of gravity of the filled bucket is above the line between the trunnions 63, the bucket will-dump by lowering the ball 44 by means of the chain hoist 43. The hot calcined rock is thereby discharged into the hopper B and is then discharged through the processing the calcined product as it is withdrawn into a bucket or basket 38 positioned on the platform 48a at loading station A.

In the calcining plant which is now in operation in accordance with the'principles of this invention, each of the buckets 38 is large enough to hold about two tons of calcined gypsum. The filled bucket 38 is then lifted from the platform 48a by the overhead crane t3 and deposited within one of the calciners or calcination chambers ill, from which the cover has been previously removed. The cover is then replaced on the calcination chamber as above indicated and tightly sealed thereto by rotating the cover by rocking the handle 22 so that the lugs it on the cover fit under the inwardly extending lugs H on the ring M. After the cover chamber it through the dralnpipe I which is controlled by the trap i3.

- While the first charge in the first calciner is undergoing calclnation, similar buckets are filled,

as above described, and introduced into other calciners which may be arranged in the manner indicated in Fig. 2. After the calcination has been completed in the first charged calciner, the steam is turned off and the pressure in the chamber is released. The cover It is then unsealed by rocking the handle 22 mounted on the shell I5 and the cover is lifted away from the top of the calciner by means of the chain hoist Bl mounted on the arcuate crane 29. The bucket containing the hot calcined gypsum is then removed from thecalciner Ill by means of the overhead. crane 43 and another bucket containing a fresh charge I of uncalcined gyp rock is introduced the calciner l0 and the calcination cycle is repeated.

- for mixing in additives, etc.

grizzly screen 61 and the gate 65 into the calcined rock storage bin 51. bin 51 is preferably heated by the steam jacket 59 in order to prevent the steam present in the hot calcined rock from cooling and rehydrating the calcined hemihydrate. After the discharge of the hot rock into the-hot storage bin ill, the calcined rock is deposited on a belt conveyor 68 and discharged into a rotary drier 69 wherein the excess steam within the main body portion of the hot rock is driven therefrom, thereby producing a dry calcined product. From the rotary drier 69 the lumps of calcined gypsum are discharged into a grinding mill Ill whereafter it is discharged onto. a screw conveyor ii, and then to an elevating bucket conveyor 12, and a horizontal screw conveyor 73 to any desired point of use. If desired, instead of passing from the conveyor 12 t0 the conveyor 73, the ground plaster may descend through a duct 74 to a tube mill 15 where it is ground to a further degree of fineness. An elevating bucket conveyor it leads from the tube mill 1! to further processing equipment,

such as an air separator, regrinders, apparatus The conveyor it may connect with the conveyor 13 so that the calcined product may by-pass the tube mill it if desired.

It has been found that by using nine calciners with a calcination cycle of 6%. hours, wherein each bucket contains two tons of calcined rock, the output of the plant is about three tons of calcined plaster per hour. It is preferable to have one more bucket for holding the gypsum than there are calciners so that'one bucket may be in The calcined rock storage the process of being dumped and refilled while a all of the calcining chambers are in operation.

In accordance with one embodiment ofthis invention, the bucket or basket for holding the gypsum in the calciner may be provided with a pair of bottom discharge doors which are hingedly secured to the side walls of the bucket.

Referring now more particularly to Figs. 8 and 9, a bucket is there shown having a substantially square cross-section and upwardly converging sidewalls 80. The bucket is open at the top and provided at the bottom with a pair of discharge doors 82 which are hingedly engaged with the side walls '60 of the bucket. These bottom doors are preferably perforated in order to permit the passage of steam and water of condensation therethrough and are provided with a suitable latch 84 in order to hold them in closed position. whereby a charge of gypsum rock is retained within the bucket when loaded.

The latch 8% is constructed so that it may readily be tripped open in order to permit the discharge of the calcined material therefrom. The

side walls so of the bucket are provided with a lifted into and out of the calciners or calcination chambers in the manner hereinbefore described.

In the modification of .the bucket shown in Figs.

' 8 and 9, the bucket has a square or rectangular "bers arenot necessary because of the relatively low steam pressures under which the gypsum is calcined by the process.

In Fig. 10 is shown still another modification of this invention. A horizontally extending calcination chamber or calciner 90 having a general cylindrical shape is provided with a hinged end door 92 which may provide a pressure-seal for the chamber. Within the calcination chamber 90 is positioned a pair of tracks 94 which are adapted to carry one or more trucks 98, each of which latter serve to support a bucket or basket 98. The buckets 98 may be rolledinto the calclner til over retractable tracks I and onto the track 96 within the calciner. The retractable track 8% is capable of being withdrawn from the opening of the calciner 9t so that the door t2 may be closed and the gypsum rock within the buckets as can be calcined in the manner hereinbefore described. It will of course be clear that suitable means may be provided for filling and dumping the buckets 98. The calciner 9t maybe constructed to hold only one bucket charged with gypsum rock or it may be constructed to hold any number of them.

The method and apparatus disclosed in .this

. application are very useful for the pressure-calcination of gypsum inasmuch as sticking of the lump material in the calciner is entirely avoided.

Furthermore, the hot material in the baskets or buckets may be quickly dumped into the heated receiving bin without loss in temperature so that substantially no cooling of parts of the calcined rock mass is permitted prior to drying. Such cooling before water-removal is undesirable because it results in the partial rehydration of the mass, resulting in non-uniformity and lowering of the quality of the product. The type of apparatus used herein also avoids the necessity of providing a tall building for housing of the apparatus as is necessary with others that have been for drying or otherwise treating materials which have a tendency to retain absorbed water or water of crystallization.

While a particular embodiment of this invention is shown above, it will be understood, oi course, that the invention is not to be limited thereto, since many modifications may be made.-

and it is contemplated, therefore, by the appended claims, to cover any such modifications as fall bucket having a perforated bottom and arranged to be supported within said chamber, means for introducing steam under pressure into said chamber, and means for withdrawing water of condensation from said chamber.

2. In an apparatus for producing pressurecalcined ypsu a calcination chamber having an open top, a removable cover normally closing the top of saidchamber in pressure sealing relationship, a crane for lifting said cover, a bucket having. a perforated bottom, said bucket being arranged to fitwithin said chamber but spaced from the side walls thereof, means for passing steam under pressure into said chamber, and a second crane for moving said bucket into and out of said chamber.

3. In an apparatus for producing pressurecalcined gypsum, a calcination chamber having an open top, a removable closure for said chamber, a perforated bucket in said chamber, means associated with said chamber and bucket for supporting said bucket in spaced relation to the walls of said chamber, means for introducing steam wherein steam and moisture are separated from v the hot calcined gypsum rock and finally comminuating the hot calcined product.

5. A process of calcining a body of gypsum rock which includes the steps of removing fines from the rock to be calcined; loading the resulting rock into a receptacle; transporting the receptacle and rock bodily into a calcination zone; introducing steam under pressure into said calcination zone for a time to efiect unii'orm calcination of said gypsum rock; removing said calcined gypsum rock and said receptacle bodily from said calclnation zone; discharging said calcined rock from said receptacle while still hot into a heating zone whereby steam is expelled from the rock to prevent rehydration thereof during subsequentcoolins: and finally comminuting the resulting mass to produce a finely divided, uniformly calcined product.

6. In an apparatus for producing pressurecalcined gypsum, a calcination chamber having tionship, a bucket disposed within said chamber,'

said bucket having a perforated bottom spaced within the true spirit and scope of this invention. p

I claim; I 1. In an apparatus for producing pressurecalcinedgypsum, a calcination pressur chamber 'having'a removable cover at the top thereof, a

from the bottom of said chamber and having side walls with outwardly and vertically extending flanges secured thereto and in a central portion. thereof whereby positively to space said side walls a from the walls of the chamber, means for introducihg steam into said chamber, means for withdrawing water of condensation from said cham- HEINRICH C. JESSEN. 

